Research Of Fine Characteristics Of Radar Radial Wind During Summer Heavy Rain

Presently,as the refinement level for severe convective weather prediction products improves continually,requirement for fine monitoring in wind field also increases gradually.Doppler weather radar is an important means for detecting the fine meso-micro scale structure of wind field,which has high spatio-temporal resolution. Studies show that many meso-micro scale systems have unique features in radial wind field.However,due to the cognitive difficulty and complexity of information extraction,the application of radial wind is mostly limited to qualitative analysis,and quantitative analysis also has some limitations.In order to develop new method for interpretation products by making full use of Doppler radar fine monitoring data,the paper focuses on extracting dynamic information qualitatively and quantitatively in summer heavy rain,then summarizes the classification.Thus,it can grasp the local fine dynamic structure and evolution characteristics of strong system in radial wind.Furthermore,FNL reanalysis data and simulative data of WRF model are used to compare with radial wind.By analysing the differences and relation between radial wind and the large scale wind,also the meso-micro scale wind,respectively,it enhances the ability in reflecting local fine features of wind field by radial wind.This paper emphasizes on reflecting the basic features of original radar wind,which provides actual and objective information in warning and forecasting for heavy rain as far as possible.The following are the main conclusions and results:(1) Doppler radar radial wind data has certain difficulties in application because of velocity ambiguity,distance folding,and observation noises,etc.Thus,considering its specific distribution,colour and texture information,etc,data preprocessing mainly contains velocity dealiasing,mean filtering,denoising,etc,of which the regional growth technology of image processing methods is applied to denoising processing.It turns out that lots of noises are filted,while effectively remaining the original structure,and the quantitative calculation of wind field structure can be implemented as well.(2) On the basis of data preprocessing,stream function and velocity potential are applied to radial wind field,which can effectively extract the information,such as convergent movement and rotational motion,based on the inherent features in radar volume scan.Then,the typical dynamic characteristics of radial wind during heavy rainfall is summarized:the convergent movement and rotational motion of radial wind begin from lower layer.With convergent layer uplifting,getting deeper and the rotational motion strengthening,precipitation gets heavier.When convergent layer decreases,and the cyclonic rotating motion weakens,rainfall tends to reduce. Studies show that radial wind can provide not only visualized and real-time distribution of local wind in the mid-lower layers from other perspective,but also a certain indicative significance in warning and forecasting for severe rainfall.(3) By comparing radar radial wind with the large scale wind in short-time strong rainfall,it focuses on analysing their reflections in strong precipitation systems,respectively,and their relations.The large scale wind is helpful to understand the environment of which the meso-micro scale systems generate and develop,the dynamic condition of moisture transporting and convergenting,etc.While radial wind can monitor the local structure and evolution of systems in time,also provide quantitative information.And to some extent,it provides further information and details for background wind field.(4) By comparing the wind field of WRF model with radial wind,the similarities,differences,and mutual assistance relation between them are studied.The model wind is helpful to grasp the movement route and strength of precipitation systems,it can also give the future trend,but the refinement level and stability has certain limits.Radar wind offers timely and objective information of local dynamic condition,but it only displays partial information of actual wind.So,it should combine with model data to reflect the meso-micro scale features of wind field,and to describe local heavy rainfall systems from different perspectives.